Leakproof bottom closure for single wall bag



LEAKPROOF BOTTOM CLOSURE FOR SINGLE WALL BAG Filed June 5, 1964 Nov. 15, 1966 F. R. BECKER m 2 Sheets-Sheet 1 Fig.

AGE/VT Nov. 15, 1966 BECKER 1 3,285,498

LEAKPROOF' BOTTOM CLOSURE FOR SINGLE WALL BAG 2 Sheets-Sheet 2 Filed June 5, 1964 Fig. 3

m r T 6 N k E C v 6 m 5 Q M H 0 m F AGE/VT United States Patent LEAKPROOF BOTTOM CLOSURE FOR SINGLE WALL BAG Frederick R. Becker III, New Orleans, La., assignor to West Virginia Pulp and Paper Company, New York, N.Y., a corporation of Delaware Filed June 3, 1964, Ser. No. 372,173

4 Claims. (Cl. 229-57) This invention relates to leakproof bags and particularly relates to single-wall paper bags which are substantially impervious to liquids and have utility as wastedisposal bags.

Leakproof paper bags which can resist moisture and which can particularlj resist exposure to weather are useful for many applications such as packaging of wet vegetables and disposal of waste materials. Bags which are sufficiently leakproof to contain liquids for a prolonged period, such as several days, are satisfactory for packaging of very dusty materials, for packaging of iced sea foods, and as an outdoor receptacle for household garba e.

i waste disposal bag for household garbage requires wall and bottom surfaces which are substantially impervious to liquids and tough enough to prevent puncture by protruding objects. The side and bottom seams must be leakproof and also must be strong enough to withstand impact shock from waste being thrown therein. The bag should be of readily expandable construction in order to accommodate bulky objects and of deep-gusset construction to avoid damage to bottom corners.

A waste disposal bag having adequate leakproof characteristics may be utilized as a household garbage can, as food waste receptacles in cafeterias, restaurant kitchens, bakeries, and food processing plants, as refuse disposal units in hospitals where sanitation is vitally important, as industrial waste receptacles in factories, and as trash receivers in roadside parks and other picnic and amusement areas.

A thorough feasibility test in four representative cities, covering in all more than 2,000 premises, was conducted by the American Foundation, 1313 East 60th Street, Chicago 37, Illinois. The research project, No. 115, was made with the cooperation of the Research and Development Committee of the Kraft Paper Association, Inc. Its findings were published in August 1963, as a 39-page report, Paper Bags for Household Refuse Handling. It was concluded that the disposable kraft paper refuse sack system is a contribution to the art, a step in the right direction and one worthy of serious consideration by many cities.

A paper waste disposal bag is usually pendently supported in upright position with its top open for convenient disposal of waste therein and with its bottom out of contact with a supporting surface. Considerable impact and static load stresses are consequently placed upon the bottom of the bag and especially upon the bottom seam itself when refuse is put therein. Bags now being used are generally of gusset construction and obtain needed strength from binding strips which are bent over the flattened bottom ends of the bags and sewn together as shown in US. 1,752,292, for instance.

The paper waste disposal bags of this invention are also of gusset construction but have bottom surfaces which are both strengthened and sealed with a hot-melt thermoplastic material; no binding strips are needed and no stitching is required. Deep gussets are generally preferred in order to accommodate bulky materials. The paper used in manufacturing the bags must be capable of heat sealing on one side. The paper is preferably coated with a continuous film of a thermoplastic material in- Public Works Association Research,

Patented Nov. 15, 1966 "ice order to make the paper impervious to liquids and capable of self-sealing to create an internal leakage barrier. A satisfactory type of thermoplastic film is polyethylene of one-mil thickness. Water resistance may be enhanced by wet-strength sizing, for example.

This invention of a leakproof bottom closure for a single wall bag is novel because of its sealed-in gussets, because of the terminus of its longitudinal seam being totally enclosed, because of its placement of a quicksetting adhesive athwart the length of the bag to create an extensive barrier against leaks at gusset terminal edges and to distribute stresses more evenly, and because the two faces of the bag are separately adhered with adhesive to one of the faces after folding. Novel characteristics of the sealed-in gussets are placement of gusset terminal edges inside of paper surfaces on either side of the gussets and sealing of these gusset terminal edges and of the opposed front and back paper surfaces to each other without placing load stresses upon the seal. Placement of the longitudinal seam terminus between the folded bottom surfaces is an essential feature of this invention and is necessary to attain leakproofness. The invention can be more thoroughly understood by referring to the drawings, FIGURES l6. In these figures, the single-wall bag having the novel bottom closure described herein is shown upside-down, with its bottom toward the top of each sheet; descriptions of bag structure refer to bag positions as shown in these figures.

FIGURE 1 shows the pattern used in cutting the bottom edge of a flat strip of paper whose parallel longitudinal edges are to be joined with an adhesive to form a tube, future gusseting folds being shown as dashed longitudinal lines, and future bottom construction folds being shown as dashed transverse lines. The heat-sealable side of the paper must be uppermost as shown if the flat strip of paper is to be formed into a tube with its longitudinal seam uppermost.

FIGURE 2 shows the flattened tube during that part of the manufacturing process, after gussets and a transverse primary leakage barrier have been formed by heatsealing, when the front flap is being folded down again into parallel contact with the back flap and on top of a freshly-applied first sealing strip which closes off the ends. of the gussets and forms a transverse secondary leakage barrier across the entire bottom of the bag.

FIGURE 3 shows the flattened tube with the front flap having been flattened on top of the first sealing strip, with two additional parallel strips of adhesive having been deposited upon the front flap, and with one additional strip having been deposited upon the back flap.

FIGURE 4 shows the bag of FIGURE 3 after the entire terminal zone bearing the adhesive strips has been folded over upon the front face of the bag, with crosssections for FIGURES 5 and 6 indicated, whereby the strong, leak-proof bottom of the bag is formed.

FIGURE 5 shows a cross-section, highly magnified as to thickness, of the glued bottom of the bag between the gussets ,as indicated in FIGURE 4.

FIGURE 6 shows a cross-section, highly magnified as to thickness, of the glued bottom of the bag in a gussetted portion, as indicated in FIGURE 4.

After having been cut to form the transverse edge pattern shown at the top of FIGURE 1, the paper strip is folded longitudinally to enclose the heat-sealable side, and the outside longitudinal edges of the front faces 12a, 12b, are adhesivelyoverlapped to define longitudinal seam 23 and form a flattened tube, having a front face 12, which is uppermost in FIGURES 2, 3, and 4, and a back face 11. The end portion of the back face 11 is a relatively long back flap ;16. The end portion of the front face 12 is a shorter front flap 17 shown as 17a, 17b in FIGURE 1. Longitudinal fold lines 26, 27, 31, 32, 33, and 34, shown prematurely in FIGURE 1 by dashed lines, are made in the tube, and gussets 14, are formed. Longitudinal lines 31, 32 define the back face 11; longitudinal lines 33, 34 define the front face 12;and longitudinal lines 26, 27 define inward penetrations of the gussets 14, 15.

A transverse score is made along fold line 24 for temporary folding of the front flap 17, and another transverse score is made along fold line 25 below line '24 for permanent folding of both front and back faces 12 and 11, as shown in FIGURE 2. The front flap 17 is heat-sealed to the back flap 16 in a transverse path 35 parallel to and between fold lines 24 and 25 to create an internal primary leakage barrier by cohering the back flap 16 to the front flap 17 in the area between the guessets 14, 15 and each flap 16, 17 to the walls of the gussets 14, 15in the gusset areas.

Then the short front flap 17 is temporarily folded forwardly toward the front face 12. While the short front flap 17 is folded over upon the front face 12, a quick-setting adhesive, such as a hot-melt adhesive, is applied generously in a continuous straight line as a transverse gusset seal strip 36 contiguous to this fold line 24, as shown in FIGURE 2, so that the hot liquid comes into contact with the back flap 16, the gusset terminal edges 19, 20, and the inner surface of the front flap 17 along the fold line 24. As the front flap 17 is folded back again upon the back flap 16, as indicated in FIGURE 2, the adhesive strip 36 is flattened, and the relatively fluid adhesive along thi strip 36 is forced into the folds of gusset terminal edges 19, 20, forming an internal secondary leakage barrier.

As may be seen in FIGURE 3, these three distances, measured longitudinally, may be considered as three incremental steps and should be approximately equal in order to obtain optimum effectiveness as to the paper usage and bag strength: 1) from the terminal edge of back flap 16 to the terminal edge of front flap 17; (2) from the terminal edge of front flap 17 to the terminal edges 19, 20 of gussets 14, 15; and, (3) from these terminal edges 19, 20 to fold line 25. The most satisfactory step distance Was found to be one-half inch. However, the distance from gusset terminal edges 19, 20 to fold line may be a little greater than the other two steps, such as /8 inch. A larger or smaller distance than /2 inch may be used for each step, such as inch or inch, but an excessive distance wastes paper and adhesive, and an inadequate distance can create difiiculties as to accurate cutting and folding.

With the short front flap 17 flattened into face-to-face contact with the back flap 16 and forming :a linear extension of the front face 12, additional strip-type applications 39, 38 37 of a quick-setting adhesive, such as a hot-melt adhesive, are conveniently made upon the outer surface of the front flap 17 and the inner surface of the back flap 16. A primary load strip 39 is applied transversely onto the front flap 17 between the temporary front face score line 24 and the bottom score and fold line 25 in order to take as much stress as possible from the inner gusset seal strip 36 and from the inner heatsealed strip 35 which is approximately beneath load strip 39. A secondary load strip 38 is applied transversely onto the front flap 17 between the temporary score line 24 and the terminal edges of the front flap 17 to secure the front flap 17 to the front face 12 and to seal the bag more effectively. Finally, a load-and-seal strip 37 of quick-setting adhesive is applied to the back flap 16 between the terminal edge of the front flap 17 and the terminal edge of the back flap 16.

The tube having been scored at the transverse line 25, parallel to and below the score line 24, the combined back flap 16 and front flap 17 are folded forwardly along this score line 25 untilthe adhesive strips 37, 38, 39 are brought firmly into contact with the front face 12. The

4 front flap 17 and the back flap 16 are thus adhesively but separately secured along their entire widths to the front face 12. The terminus of the longitudinal seam 23, as part of the terminal edge of the front flap 17, is thus totally enclosed by paper surfaces on either side and is sealed with adhesive, whereby leakage is prevented through the terminus.

All adhesive strips 36, 37, 38, 39, are loadbearing strips to some degree, but load strips 38, 39 particularly support the front flap 17, and strip 37 supports back flap 16 with some assistance from strip 36.

If adhesive fluidity is low enough to keep the strips separated, internal heat-sealed barrier 35 and external sealing strips 36, 37 provide multiple protection against leaking, and rupture of the load-bearing strips 37, 38, 39 is minimized by separately securing the back and front flaps 16 and 17 to the front face 12.

Because of high sealing pressures and high fluidity in the adhesives generally used, the adhesive strips '37, 38, 39 are likely to coalesce into a single adhesive sheet extending from the edge of the fold line 25 approximately to the terminal edge of the back flap 16. This result can be accomplished, of course, by using a different number of transverse strips of varied width for depositing an adhesive possessing greater or lesser fluidity. After heatsealing to form the primary leakage barrier 35 and depositing the adhesive strip 36 to form the secondary leakage barrier, another useful procedure is to deposit a sheet of quick-setting adhesive covering the entire front and back flaps 17 and 16 so that all exposed surfaces of both front and back flaps 17 and 16 can be uniformly adhered to the front face 12 when the front and back flaps 17 and 16 are folded upon the front face 12.

I claim:

1. A leak-proof single-wall bag formed from paper with a heat-sealable inner surface, said bag having a front face, a back face, and inwardly-folded gussets when in flattened tubular form and having a folded bottom formed without use of binding strips or stitching, said folded bottom comprising:

(a) a bottom fold in both front and back faces and in both gussets which extend transversely across the (b) as an extension of the back tom fold, a back flap,

(c) as an extension of the front face beyond the bottom fold, a front flap which extends longitudinally a shorter distance beyond the bottom fold than the back flap,

(d) gussets extending longitudinally a shorter distance beyond the bottom fold than the front flap,

(e) an internal primary leakage barrier, formed by heat-sealing along a transverse path across the back flap, front flap, and gussets, which coheres the back flap to the front flap and both flaps to the gussets, an

(f) an internal secondary leakage barrier, formed by applying a transverse seal strip of a quick-setting adhesive between the front and back flaps and in contact with the gusset terminal edges,

(g) a strip of a quick-setting adhesive which seals the bag bottom and adheres the back flap and the front flap to the front face.

2. A leak-proof single-wall bag formed from paper with a heat-scalable inner surface, said bag having a front face and a back face when in flattened tubular form and having a folded bottom formed without use of binding strips and stitching, said bottom comprising:

(a) gussets having transverse terminal edges,

(b) as an extension of the front face, a front flap having a transverse terminal edge extending beyond the gusset terminal edges,

(0) as an extension of the back face, a back flap having a transverse terminal edge extending beyond the terminal edge of the front fla face beyond the bot- (d) an internal primary leakage barrier, formed by heat-sealing along a transverse path across front flap, back flap, and gussets, which coheres the back flap to the front flap and both flaps to the gussets,

(e) an internal secondary leakage barrier, formed by applying a transverse seal strip of a quick-setting adhesive between the front and back flaps and in contact with the gusset terminal edges,

(f) a bottom fold whereby front and back flaps are folded into contact with the front face, and

(g) transverse load strips of a quick-setting adhesive which adhere the back and front flaps to the front face, comprising:

(1) a seal-and-load strip across the back flap, be-

yond the terminal edges of the front flap, which adheres the back flap to the front face,

(2) a load strip across the front flap, between the gusset terminal edges and the terminal edge of the front flap, which adheres the front flap to the front face, and

(3) a load strip across the front flap, between the bottom fold and the gusset terminal edges,

which adheres the front flap to the front face and supports the internal primary leakage barrier.

33. The bag of claim 2 wherein the distance from the back flap terminal edge to the front flap terminal edge approximately equals the distance from the front flap terminal edge to the gusset terminal edges, each distance being equal to or less than the distance from the gusset termnial edges to the bottom fold.

4. The bag of claim 2 wherein the terminus of the longitudinal seam is totally enclosed by paper surfaces and adhesively sealed.

References Cited by the Examiner UNITED STATES PATENTS 3/1927 Avery 22958 4/1943 Abramson 22955 

1. A LEAK-PROOF SINGLE-WALL BAG FORMED FROM PAPER WITH A HEAT-SEALABLE INNER SURFACE, SAID BAG HAVING A FRONT FACE, A BACK FACE, AND INWARDLY-FOLDED GUSSETS WHEN IN FLATTENED TUBULAR FORM AND HAVING A FOLDED BOTTOM FORMED WITHOUT USE OF BINDING STRIPS OR STITCHING, SAID FOLDED BOTTOM COMPRISING: (A) A BOTTOM FOLD IN BOTH FRONT AND BACK FACES AND IN BOTH GUSSETS WHICH EXTEND TRANSVERSELY ACROSS THE BAG, (B) AS AN EXTENSION OF THE BACK FACE BEYOND THE BOTTOM FOLD, A BACK FLAP, (C) AS AN EXTENSION OF THE FRONT FACE BEYOND THE BOTTOM FOLD, A FRONT FLAP WHICH EXTENDS LONGITUDINALLY A SHORTER DISTANCE BEYOND THE BOTTOM FOLD THAN THE BACK FLAP, (D) GUSSETS EXTENDING LONGITUDINALLY A SHORTER DISTANCE BEYOND THE BOTTOM FOLD THAN THE FRONT FLAP, (E) AN INTERNAL PRIMARY LEAKAGE BARRIER, FORMED BY HEAT-SEALING ALONG A TRANSVERSE PATH ACROSS THE BACK FLAP, FRONT FLAP, AND GUSSETS, WHICH COHERES THE BACK FLAP TO THE FRONT FLAP AND BOTH FLAPS TO THE GUSSETS, AND (F) AN INTERNAL SECONDARY LEAKAGE BARRIER, FORMED BY APPLYING A TRANSVERSE SEAL STRIP OF A QUICK-SETTING ADHESIVE BETWEEN THE FRONT AND BACK FLAPS AND IN CONTACT WITH THE GUSSET TERMINAL EDGES, (G) A STRIP OF A QUICK-SETTING ADHESIVE WHICH SEALS THE BAG BOTTOM AND ADHERES THE BACK FLAP AND THE FRONT FLAP TO AND FRONT FACE. 